Method of drilling lateral bores



March 14, 1944. J A, zuBLm METHOD OF DRILLING LATERAL BORES Filed Jan. 27, 1942 INVENTOR. rib/1w A. ZUEL/N, QMW

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Patented Mar. 14, 1944 UNITED STATES PATENT OFFICE METHOD or DRILLING LATERAL Bones John A. Zublln, Los Angeles, Calif. Application mm 21, 1942, Serial No. 428,409

. 2 Claims.

This invention relates to the drilling of angular holes which originate and terminate within the oil sand and which emanate with-sharp deviations from the vertical well bore penetrating this sand. 1

In my prior application, "Method and means to drill deviating holes," Serial No. 423,227, filed December 16, 1941, I have described a method and means to drill lateral bores, said bores being curved or straight, consisting of the provision of a flexible resilient guide having a curvature substantially equal to the desired curvature of the bore. Said flexible resilient guide is held stationary in the curved bore being produced while the bit is rotated either by a turbine or by a flexible hollow shaft. To drill a straight extension of a curved bore so produced, a normally straight resilient drill guide is inserted in the curved bore and the bit on the end thereof rotated .by any means desired causing it to drill a substantially straight bore.

The above patent application fully describes this process, particularlythe drilling or the curved bore, the subsequent withdrawal of the normally curved flexible resilient guide, and the insertion thereafter of the normally straight flexible resilient guide. The insertion of the straight drill guide into the laterally curved bore cannot, however, be accomplished without additional means to force the normally straight drill guide into this curved side hole, for the reason that due to gravity the normally straight drill guide hangs freely within the vertical well bore with no energy whatsoever to force it into the wall of the bore in the direction and at the place where the curved side hole leaves the vertical bore. Previously, I have contemplated using conventional deflecting means, such as whipstocks and the like, to be set in the well bore where the deflecting bore starts. In many cases, however, this procedure is complicated, expensive and difficult to apply, particularly-when lateral bores are required extending in different directions from one and the same well bore. I have therefore made the invention herein explained which comprises methods of entering curved side holes without the use of such tools,-in order to simplify the method of drilling straight holes out of curved side holes. i J 1 The resiliency and flexibility of drill guides made of helically slotted pipe of proper steel as described in my application Serial No. 423,225, filed December 16, 1941, entitled "Flexible resilient drill pipe," is very great. A normally slightly curved drill guide of these characteristics is run into the well after the curved side hole has been drilled. The resiliency and curvature of the guide are sufficient to drive the bit towards one side of the well bore so that, when the bit reaches the depth at which theside hole starts,the bit will, upon proper orientation of the drill pipe from the surface, readily fall into the mouth of the side hole, whence it can be lowered to the end of the curved side hole where the straight hole is to be started. If now the bit and this slightly curved resilient drill guide are rotated, then the bit will start to make hole.

Different bits have different cutting motions. Some of-them will drill more forwardly in the direction of the axis of the well bore. while others have cutting edges on the side, enabling them to penetrate forwardly and sidewise at the same time. Any drilling bit will follow the way of least resistance, and the rotating slightly curved resilient drill pipe will have a natural tendency to rotate the bit around an enlarged circle, due tothe side pressure which the normally curved resilient pipe exerts on the bit in a straight hole. The resiliency of the guide, the type of the bit, the number of revolutions of bit and guide, and the characteristics of the flarmation can be related in such a manner as to predetermine the desired size of oversize hole which the bit is supposed to drill,

The straightness of the hole is not affected by the normal curvature of the resilient flexible drill guide because its curvature in one direction is offset by its curvature in the opposite direction after one-half of a turn of the guide itself.

Although it is contemplated to use for the drilling of the straight hole a flexible resilient drill pipe of normally less curvature than the drill guide used to drill the originally curved hole, it is possible to use the curved drill guide utilized for drilling the curved hole without rotation for drilling the straight hole by rotating this curved drill guide. It is therefore to be understood that the elongated normally curved guide is flexible and resilient enough to be rotated not only in a straighthole but also in the curved hole which has been previously drilled.

With the above in mind, it is the primary object of the present invention to provide an improved method to cause a bit with an elongated resilient guide to enter an existing curved side hole in a well bore without the help of deflecting tools set in the well bore.

,It is another object of the present invention to provide an improved method and means for drilling astraight extension from a sharply curved lateral bore.

It is a further object-of the present invention to provide a method for cutting a straight bore with the same equipment which previously has been used to drill a curved lateral bore.

It is a further object of the present invention to provide a method and means or producing a lateral straight bore which is of greater diameter than the bit.

It is a further object of the present invention to permit customary rotative speeds in the drilling of straight lateral bores which enables the use of customary drilling tools.

It is a further object of the present invention to provide a novel method for underreaming well bores.

Other objects and advantages will become apparent as the description proceeds.

Turning now to the drawing:

Figure 1 is a diagrammatic view of one form of the present invention shown in a well, with the bit about to enter a lateral bore;

Figure 2 is a view similar to Figure 1 illustrating the production of a straight, enlarged extension of a curved side bore;

Figure 3 is a section of the lower end of a modified form of a device such as shown in Figure 1; and,

Figure4isasectionsimilartoFigure3ofa further modified form of the device shown in Figure 1.

Referring first to Figure 1, the method by which a bit and guide are caused to enter a lateral bore has been shown. The well it has a lateral bore ll into which it is desired to have a bit and a fiexible resilient guide enter for further drilling. The flexible guide is indicated at l2 and is'secured to either the drill pipe or another length of flexible pipe I! by means of the coupling M. The lowermost end of this fiexihle guide I2 carries a bit It which may be rotated by a turbine, at flexible shaft, or by rotation of the guide l2. It can be appreciated that, if the guide were straight, the bit I! would not enter the side bore II as the entire apparatus is lowered into the well ll, because gravity would normally cause the bit to pass the mouth of the side bore II and continue to the bottom of the well. For this reason. the resilient guide l2, instead of being normalLv straight, is provided with a curvature in its length. This curvature need not be as great as that which was necessary to produce the bore II. It need be, for example, only sufiicient to cause the guide I2 to take the configuration shown in dotted lines in Figure 1 except when restrained by the walls of the well I0. If the flexible guide is properly oriented in the well bore by any suitable known method, it can be seen that lowering the bit and guide will cause the bit to travel along the outside surface It of the lateral bore until the bit has entered the mouth of the bore I I. After such entry the hit can be forced to the end of the lateral bore and drilling may proceed.

As the guide I2 is normally curved, rotation of the bit I! while the guide I 2 remains stationary would result in the production of a curved bore as described in my application entitled "Method and means to drill deviating holes" mentioned above; If it is desired to drill a straight bore,

it becomes necessary to utilize some method of operation which will cause the bit on this curved 2 the guide l2 has been shown in the curved bore II and, as shown in this figure, the bore has been continued from the point 20 with a substantially straight axis. This is accomplished by simply rotating the guide l2 as drilling proceeds. As shown in Figure 2, the first efiect of drilling with a rotating guide is to cause the production of a tapered bore 2 I, which eventual- 1y merges into a cylindrical bore 22. The reason for the straightness of the bores 2| and 22 is the fact that rotation of the drill guide neutralizes the effect of the curvature thereof. The reason for the enlargement of a bore so that it is of a greater diameter than the diameter of the bit is the side pressure exerted on the bit by the turning guide l2. Continued drilling will therefore produce a straight enlarged bore.

The above described drill guide i2 has a curvature in its length suiilcient to cause it to enter the side bore II. It is possible, instead of utilizing a special curved guide, to utilize the curved guide which was used to produce the original curved portion is of the lateral bore II. In fact. it is possible to drill the curved portion is of the bore II, and then by changing the operative technique to cause a continuation of this bore in a straight line. In order to accomplish this result it is necessary that, while the portion I9 is being drilled the guide l2 be held against rotation while the bit is rotated to cut the formation. This rotation of the bit while the guide remains stationary can be accomplished by the use of a turbine as described in my above mentioned copending application. It may also be accomplished by some such means as is shown in Figure 3. In Figure 3 a resilient guide 30 consisting essentially of a helically slotted resilient pipe is provided with a rotating head 3!, which carries a bit 32 by means of the conventional pin and box connection. This head 3| is held in place on the lower end of the resilient guide 20 by mean of balls 23 running in races on the interior of the guide 30 and on the exterior of the head 3!. Rotation of the head 3| and the bit 32 without rotation of the guide 30 is accomplished by rotating an interior flexible tubular shaft 34, which is secured to the head 3| by any suitable means. This interior shaft 34 may be conveniently used to convey the drilling fluid to the bit through to interior bore 35. It can be appreciated that the curved portion of a side bore can be produced by simply allowing the exterior guide 30 to remain stationary while the shaft 24 is rotated. To produce a straight bore the shaft 34 and the guide 30 may be rotated as a unit or at different speeds as desired. The guide 30 may be most conveniently secured to the drill pipe extending to the surface while the flexible shaft 34 is secured to a smaller diameter pipe passing through the bore of the drill pipe, this smaller pipe also extending to the surface and being capable of connection to the rotating machinery there situated. However, the inner shaft may be rotated by any other means desired.

In the event that it is desired to use a curved resilient guide solely for the production of a straight bore, the construction showed in Fisure 4 ,may be used. In this form of construction the bit I! is attached to a coupling II, which is in turn threaded into the resilient guide 42. On its interioi this guide 42 carries a flexible hose 43, which is used to convey the drilling fluid to the bit. This hose is connected to a nipple 44 which is also threaded into the guide 42 and guide to make such a straight bore. In Figure serves to transmit the fiuid to the bit through a passage 45 extending through the coupling 4|. 0! course it is to be understood that the coupling, guide and hose assembl can also be used when the bit is intended to be rotated by a turbine inserted between the guide and a bit, as described in my copendin application, Method and means to drill deviating holes," mentioned above. I

With the above constructions and principles in mind, variations in operative technique readily suggest themselves. Perhaps the simplest method in drilling a straight hole is to secure the bit to the lower end of a resilient drill guide and rotate the guide and bit as a unit. However, the bit may be rotated independently of the guide as by means of a flexible hose or shaft driven from the surface or by means 01' a turbine at the lower end of the guide. If it is desired to drill a curved hole, the bit must be rotated while the normally curved resilient guide remains stationary, in which case, a turbine or some such expedient as that shown in Figure 3 must be employed. It the device in Figure 3 is utilized, the same equipment can be used for the curved and straight portions of a lateral bore by simply stopping rotation 01' the guide to produce curved bores and causing the guide to rotate to produce straight bores. Normally curved resilient guides or the construction shown in either Figure 3 or Figure 4 can be used to produce enlarged bores, even to the'extent of underreaming a well bore. The tapering and cylindrical portions shown in Figure 2 would then exist in the portion of the well bore acted upon by a rotating normally curved guide having a bit on its lower end which rotates either at the same or at diflerent speeds from the speed of the rotating guide.

I claim: a

1. The method 01' producing a bore having curved and straight portions which comprises rotating and advancing a drilling bit while resiliently and continuously urging the bit against one side wall of the bore to cause the bit to advance along a curved path to form the curved portion of the bore, and rotating and advancing the bit while resiliently urging the bit radially outward from the axis of the bore and progressively changing the outward radial direction in which the bit is resiliently urged to cause the bit to form the straight portion of the bore.

2. The method of drilling from an existing well bore a deviating ell bore having an initial curved portion and a continuing straight portion comprising flexing to reduce the curvature and thus setting up stresses in an elongated normally curved resilient drill guide, disposing said guide in the existing well bore and restraining the same flexed to a curvature substantially less than its normal unstressed curvature by contact with the walls of the existing well how, utilizing the energy expended against a side wall or the existing well bore during the return of said drill guide to its normal unstressed curved configuration for pressing a drill bit on one end of said guide into a side wall of the existin well bore, rotating and advancing the bit while holding the drill guide against rotation to drill the curved portion of the deviating bore, and thereafter and without removal of the drill guide from the curved deviating bore initiating rotation of said guide and simultaneously rotating and advancing the drill bit while rotating said drill guide to drill a straight continuation of said deviating curved bore.

JOHN A. ZUBLIN. 

